According to E.Ryerson:
> > > Running htdig/htmerge/etc. all go fine when indexing alpha characters.
> > > But, when we try and do a search on a date, or any purely numeric,
> > > nothing is
> >
> > See http://www.htdig.org/attrs.html#allow_numbers>
> sorry to be a newbie, but what file is allow_numbers in?
> i've got version 3.1.2 and greped through everything i could think of.
> i also even added allow_numbers to my htdig.conf file but htsearch still
> turns up no match for anything numerical.

You need to add

allow_numbers: true

to your htdig.conf. Then you need to rebuild your index from scratch, using
rundig (or htdig -i). When you first indexed your site without allow_numbers
set to true, none of the numbers were put into the index, so even if you
now search that index with the option enabled, there are still no numbers
to be found.